It used to be Tales of the Abyss, but I fell in love with Tales of Vesperia. The cast of heroes was fantastic, not to mention the whole RitaxEstelle pairing. <3 And then Yuri was so awesome with his vigilante style of saving the day; he's the perfect anti-hero. Oh, and Repede is cool, too. X3 The final boss battle was freakin' hard though; it wiped out my entire inventory of healing items. O.o

I'd say everything after the 1st form was hard. I remember finishing the 1st form rather quickly and thinking: "That was it?" Of course it wasn't. Damn it. X-x Oh well. I beat it, so I'm not complaining. It just took a lot of work~

To get to the Dungeon just go to Phareo's Crag before entering Zaude for the first time (if you don't then you will miss it since its a times event), enter the warp thing there and speak to the sage in Yormgen (the place you will warp to) and accept his invitation to rest. Then after you beat the game, load your save data after beating it (the one with a star at the side) and go to Phareo's Crag again to speak with the sage, you will get a book, then go to Dhangrest to watch a scene and finally go to Yumange (the Spa) and head South to see the warp thing to the dungeon.

Tales of Symphonia for gamecube was fun too; even the second one. The second one wasn't amazing cause of the over-leveling, etc; but it was still okay.